6080 no longer warming up [resolved]

[Spargle Spike]

Hello,

I finished the build on my Crack two days ago. All resistance checks and voltage checks were good, so I started listening to some amazing music. Really spectacular! Last night, the volume drained out while I was listening, and when I checked the unit, I found that the 6080 was no longer glowing. The 12au7 was still glowing. I turned it off and, after letting it cool, reseated the 6080. it worked for the rest of my listening for the night.

Today, about 1 1/2 hours into listening, I got the same draining volume and found the same situation as last night: The 6080 no longer glowing and the 12au7 still glowing. I turned off the unit and reseated the 6080 but now it won't glow.

I rechecked the resistances and they were good.
I rechecked the voltages, and they were good, except terminals 2, 4, and 13 are all showing 231V rather than the 170 they showed after the build.

Since the 6080 isn't warming up, I'm thinking the voltage test may no longer be valid but I don't have enough experience to understand the change. I tested the resistance between b7 and b8 and it was 0.

Thoughts on where to go from here?

[Spargle Spike]

Tried it again and gave a gentle wiggle to the tube while it was in the socket. It started to glow!!! The solder looked fine, but I reflowed all the connectors to be sure.  I'm happily listening to music again. Sometimes I'm Happy from And Then Again (Live).

I'll repost if it goes out again after some listening.

[Paul Birkeland]

I would pull and reseat the 6080 in the socket a few times to help scrape off any oxidation on the pins that is preventing the heaters from glowing.  Since the 12AU7 continues to glow, this is unlikely to be a soldering issue. 

[Spargle Spike]

I would pull and reseat the 6080 in the socket a few times to help scrape off any oxidation on the pins that is preventing the heaters from glowing.  Since the 12AU7 continues to glow, this is unlikely to be a soldering issue.

Thanks for taking a look, Paul. I did use a little alcohol to clean the pins, but I'm experiencing the same issue. If I wiggle it wrong, the heaters go out, and the music slowly fades. Another wiggle and it comes back. The pins are shiny. Any other suggestions?

I just put in the Speedball. Wow!!!! My wife was able to hear how awesome it sounded.

[Paul Birkeland]

You could look down into the holes in the socket itself and there are little Y shaped fork contacts or there will be round metal contacts with a cut down the middle.  These can be carefully bent inwards slightly with a very small flathead screwdriver or a small metal pick, and the tightened socket contacts may grip onto the heaters a bit better.  This would be the contacts on B7/B8 on the 8 pin socket.

It's also worth mentioning that it is possible (though unlikely) that the green wires on B7/B8 are all well soldered together but somehow not well soldered to the socket itself, so I'd also verify that the solder is well flowed out on those connections as well.

[Spargle Spike]

Great. I'll check it out. I reflowed the connections yesterday; they are very shiny. If the gentle socket bending doesn't work, I'll try it again.

Thank you!   

[Spargle Spike]

I think it might be the tube. The glass twists ever so slightly in the base. Rotating it slightly in the base will make it glow if it isn't.

[Paul Birkeland]

Ah, well if you can hold it in the position where it's working properly, then drip superglue down between the base and the glass, you may be able to anchor it so it doesn't have that freedom to move.  Still, that kind of movement would be indicative of a loose socket connection or maybe a loose socket pin contact.